To many Americans, that painful morning 11 years ago today still feels raw.

Others have no memory of what unfolded.

San Diegans such as Jasmine Fontenot and Everett Jordan, now both 13, were toddlers when a band of terrorists launched attacks on the United States using commercial airliners, resulting in the deaths of nearly 3,000 people at the World Trade Center in New York City; the Pentagon in Arlington, Va.; and near Shanksville, Pa.

Everett was too young on Sept. 11, 2001, for any of the tragedy to sink in at the time: How the hijackers steered American Airlines Flight 11 and United Airlines Flight 175 into the twin towers. How they plunged American Airlines Flight 77 into the Pentagon. How they likely intended to navigate United Airlines Flight 93 right into the U.S. Capitol in Washington, D.C., before passengers tried to regain control of the cockpit, leading to a crash in a field.

Today, Everett knows this much: “9/11 was one of the worst tragedies in our history,” he said Monday amid a classroom discussion on the topic at Innovation Middle School in Clairemont.

Schools across the nation today will mark the 11th anniversary of the attacks with memorials, moments of silence and guest speakers, along with special lessons that are evolving as the years pass and the immediacy of the event fades.

Rick Selby, an 8th-grade social studies teacher at the school, said he increasingly approaches 9/11 as more of a moment in history than as a current event. He said that until a couple of years ago, his students had shared personal memories and feelings about the day.

His current crop of students, including Jasmine and Everett, are too young to recall the event, so his anniversary lesson plans have “gone from reflection to instruction. To these guys, it’s like World War II.”

Discussing the worst terrorist incident on U.S. soil can be a challenging task in the classroom, said Celine Provini, editor of the San Diego-based company EducationWorld, which offers 9/11-related lesson plans to teachers nationwide.

“Talking about 9/11 means talking about scary topics like terrorism, death and war, as well as tricky issues such as discrimination and religious and cultural differences,” she said. “Teachers are often hesitant to start conversations on these topics for fear of scaring kids or not being able to respond appropriately to their questions.”

On Monday morning, Selby carefully walked his students through a nearly hourlong lesson aimed at fleshing out what occurred, how it happened and the gravity of it all.

He started by asking his middle-schoolers what they knew about the attacks.

One student said “mad Arabians” assaulted America with planes.

Another said terrorists barreled a single aircraft into New York’s World Trade Center.

Another said no, it was two planes — and that a third plane crashed into the Pentagon.

Selby showed a video that provided an overview of the day. It mentioned how extremists tied to al-Qaeda and its leader at the time, Osama bin Laden, boarded the four commercial airliners and commandeered them.

He offered up more numbers.

Each of the towers at the World Trade Center was 110 stories tall, much taller than the highest building in downtown San Diego.

“I didn’t know they were that big,” said student Isaiah McDaniels, 13.

Some 125 people inside the Pentagon died.

Even though she had heard about 9/11 during previous years from family members, Jasmine said, “I didn’t know (the terrorists) attacked the Pentagon.”

Jack Brandais, a spokesman for the San Diego Unified School District, spoke briefly to Selby’s class about serving on a federal disaster response team in the wake of the tragedy.

In addition, Selby asked his students to analyze American political cartoons stemming from the attacks, which he used as a springboard to touch on the surge in patriotism after 9/11, along with the discrimination that arose against Muslims and others with ties to Islam.

And he gave his students a homework assignment — write a poem or letter or draw a cartoon that answers this question: How will you remember 9/11?

“You guys were 2 or 3 years old when it happened,” Selby pointed out.

“It’s important to learn about it,” his student Everett said later. If he had been aware enough to know it was unfolding, he said, “I would have been very afraid that it would happen again.”